Combining Soft Decisions In A Weather Band Radio

ABSTRACT

According to one aspect of the present invention, an apparatus is provided to enable weather band radio signals to be received and processed using a digital signal processor (DSP). The DSP can include functionality to implement both frequency modulation (FM) demodulation and weather band data demodulation, i.e., specific area encoding (SAME) demodulation. In one such embodiment, soft decision samples of a SAME message can be combined, and based on a combined result, a hard decision unit can generate a bit value of weather band data.

This application is a divisional of U.S. patent application Ser. No.12/002,067, filed Dec. 14, 2007, the content of which is herebyincorporated by reference.

BACKGROUND

Weather band radios enable a user to tune into National Oceanic andAtmospheric Administration (NOAA) weather radio (NWR) communications. Inthe United States, regions have one or more weather radio stations thatprovide continuous radio broadcasting of weather conditions. This can beespecially useful in case of weather-related or other emergencyscenarios.

The weather broadcasting occurs in a relatively narrow bandwidth of theradio frequency (RF) spectrum. Specifically, a total of 175 kilohertz(kHz) bandwidth is available at between 160.4 Megahertz (MHz)-160.55MHz, allowing a minimal 25 kHz for each channel. This narrowbandoperation can complicate radio design. In contrast, frequency modulation(FM) radio allows for much wider bandwidth for each channel, allowingmuch greater headroom for design of an FM receiver.

Currently available weather radios have been developed using analogradio technology which, although technically feasible, can be expensiveto build, is not readily miniaturized to a small form factor, and hasrelatively minimal programmable capabilities.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an apparatus isprovided to enable weather band radio signals to be received andprocessed using a digital signal processor (DSP). In one suchembodiment, a receiver may include an analog front end to receiveincoming weather band radio signals. The front end can include an analogmixer to mix the incoming weather band radio signals with a controllableoscillator frequency to generate a complex downmixed signal, and ananalog-to-digital converter (ADC) to convert the complex downmixedsignal to a digital signal.

The digital signal can be provided to the DSP, which can includefunctionality to implement both frequency modulation (FM) demodulationand weather band data demodulation, i.e., specific area encoding (SAME)demodulation. In one such embodiment, the SAME demodulator may include acombiner to receive a soft decision sample of a SAME message and tocombine it with a value in a buffer, depending on which frame of theSAME message is received. The SAME demodulator may further include ahard decision unit to receive the combiner output and generate a bitvalue.

Yet another aspect of the present invention is directed to a method forreceiving a sample of a frame of a SAME message, determining if thesample is of a first frame of the message, writing the sample to abuffer entry if so, otherwise combining the sample with a buffered valuein the buffer entry, and writing the combined result back to the buffer.The result can also be provided to a hard decision unit fordetermination of a hard decision based on the result. In someembodiments, the result is provided to the hard decision unit if thecombining is of a third frame sample and the buffered value, otherwisethe result is written to the buffer.

Yet another aspect of the present invention is directed to a system thatincludes a DSP or other programmable processor to handle digitaldemodulation of weather band signals. The DSP may include hardware thatis controlled by software, firmware or combinations to receive an FMdemodulated signal and obtain weather band data from the signal. In thisregard, the DSP may include an interpolator to receive samples ofmultiple frames of a message and generate soft decisions therefrom and acombiner to combine the soft decisions of the multiple frames into ahard decision corresponding to a bit of the weather band data. Stillfurther, the DSP may include a timing controller to control a samplingrate of the interpolator based on preamble detection. In one embodiment,the timing controller includes a timing error detector coupled to anoutput of the interpolator to control the sampling rate to be at amaximum eye opening position and a loop filter coupled to the timingerror detector having a variable gain controlled responsive todetermination of receipt of the preamble.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a NWR message code format in whichcommunications occur.

FIG. 2 is a block diagram of a weather band radio receiver in accordancewith an embodiment of the present invention.

FIG. 3 is a block diagram of a high level view of a SAME demodulator inaccordance with an embodiment of the present invention.

FIG. 4 is a block diagram of a more detailed view of a SAME demodulatorin accordance with an embodiment of the present invention.

FIG. 5 is a detailed block diagram of a combiner in accordance with oneembodiment of the present invention.

FIG. 6 is a flow diagram of a method in accordance with one embodimentof the present invention.

FIG. 7 is a block diagram of a system in accordance with an embodimentof the present invention.

DETAILED DESCRIPTION

In various embodiments, incoming weather band radio signals may bedigitally processed using flexible digital circuitry such as a digitalsignal processor (DSP) to provide weather band information, which caninclude both voice and text information. The text information can beobtained from weather band radio signals encoded according to an audiofrequency shift keying (AFSK) modulation scheme, namely a specific areamessage encoding (SAME) digital message scheme. In various embodiments,an entire weather band radio receiver can be implemented on a singlesemiconductor die, including both analog and digital circuitry.

Before discussing a detailed implementation of one such radio receiver,a background of the weather radio spectrum and message code format is inorder. As described above, weather radio exists at a relatively narrowbandwidth. Currently, in the United States this bandwidth ofapproximately 175 kHz provides for the presence of up to seven channelseach having a 25 kHz bandwidth. The RF carrier modulation for radiocommunications is narrowband FM with +/−5 kHz maximum deviation. Inturn, the sub-carrier modulation of the message information uses AFSK.Different manners of demodulating the SAME message content can berealized. As will be described further below, in various embodiments asoft decision combining mechanism may be provided and used to obtainhard decisions for incoming SAME digital messages in a weather radiosystem.

Referring now to FIG. 1, shown is a block diagram of a NWR message codeformat. As shown in FIG. 1, message 10 includes an AFSK digital message15, which may correspond to a specific area message encoding (SAME)message having a maximum of 268 bytes. In various embodiments, threeidentical digital messages may be provided in a burst communication,each of which includes the same data repeated three times. Thus thisdigital message 15 may be demodulated and then further processed togenerate a text message suitable for display on a display of a radio oran associated display, e.g., of a video device. The SAME message isphase continuous at bit boundaries, and is transmitted at a bit rate of520.83 bits per second. Logic zero information is represented at afrequency of 1562.5 Hertz (Hz), while logic one information isrepresented at a frequency of 2083.3 Hz. The message may have afrequency deviation of between approximately +/−4 kHz to +/−5 kHz. Notethat because there is no error control/parity or stop and start bits,the message information is transmitted three times in a row.

Furthermore, the message itself may be separated into a preamble portionand a message portion. The preamble portion may correspond to apredetermined number of bits, e.g., 128 bits, that may be data with veryrich bit transitions (i.e., 10101011 repeated 16 times). As will bedescribed further below, these bit transitions may be used to acquirethe incoming message of the SAME transmission and identify asynchronization point of the preamble so that the following message canbe properly demodulated and processed.

Referring still to FIG. 1, the message code format 10 then may includean optional warning alarm tone (WAT) 20 which may be a 1050 Hz tone ofbetween approximately 8-10 seconds. Following that, a verbal message 25may be transmitted, which is also optional and may have a maximummessage length of approximately 2 minutes. This voice message may have afrequency deviation of +/−1 kHz to +/−4.5 kHz. After this verbal message25, an AFSK end of message (EOM) indicator 30 may be transmitted toindicate the end of the message.

Referring now to FIG. 2, shown is a block diagram of a weather bandreceiver 100 in accordance with an embodiment of the present invention.As described above, receiver 100 may be a single die semiconductordevice including both analog and digital circuitry. Furthermore, thevast majority of the demodulation and processing of the radio signalscan be performed digitally, allowing better sensitivity and channelselectivity. Thus as will be described further below, the majority ofthe components shown in FIG. 2 may be implemented in a DSP or otherprogrammable processing circuitry. Furthermore, channel fine tuning maybe implemented digitally to relax analog frequency accuracyrequirements. While not shown for ease of illustration, understand thatradio receiver 100 may be a multi-function device including both receiveand transmit capabilities, as well as providing functionality formulti-band operation. Specifically, embodiments may be implemented in asingle chip device for use with AM, FM and weather band transmissions.That is, the receiver may include a code store (e.g., a nonvolatilememory) including software, firmware, or combinations thereof to enablethe DSP or other circuitry to operate in an AM, FM, or weather bandmode.

As shown in FIG. 2, receiver 100 may receive incoming weather band radiosignals via an antenna 102, coupled to an analog front end of thereceiver. The front end may include a low noise amplifier (LNA) 105. Inturn, LNA 105 is coupled to an analog mixer 110 which is controlled by alocal oscillator (LO) frequency f_(LO). In various embodiments, f_(LO)may be controlled by a microcontroller unit (MCU) 190 which, as shown inthe embodiment of FIG. 2, may be an on-chip microcontroller, althoughthe scope of the present invention is not limited in this regard.

As shown in FIG. 2, the downmixed complex outputs from mixer 110, whichmay be at a low intermediate frequency (IF) (e.g., at approximately 128kHz) are provided to a programmable gain amplifier (PGA) 115, theoutputs of which are provided to an analog-to-digital converter (ADC)120 that operates at a sampling frequency of f_(ADC) and which may alsobe controlled by MCU 190, in various embodiments. The digitizedinformation is provided to a direct digital frequency synthesizer (DDFS)125 which outputs digitized complex baseband data at a rate ofapproximately 12.288 Megasamples per second (MS/s). These samples areprovided to a decimator 130, which may decimate or reduce the samplingrate to a lower rate. Specifically, in the embodiment shown in FIG. 2,decimator 130 may operate to resample the incoming data to a lower rateof 512 kilosamples per seconds (KS/s). The output I and Q data fromdecimator 130 is thus provided to the DSP of receiver 100, which maygenerally correspond to all the additional circuitry shown in FIG. 2(with the exception of digital-to-analog converter (DAC) 165 and MCU190). As such, embodiments may include an article in the form of acomputer-readable medium onto which instructions are written. Theseinstructions may enable the DSP or other programmable processor toperform filtering, demodulation, and other processing in accordance withan embodiment of the present invention.

More specifically, the incoming IQ data is provided to a digitaldecimator 140, which again reduces the sample rate in half to 256 KS/s.The sampled data is provided to a digital mixer 145 where it is mixedwith fine tuning control signals from a fine tune controller 185. Theoutput of digital mixer 145 is decimated in decimator 148 which mayreduce the sampling frequency to 64 KS/s, and which in turn is coupledto a channel filter 150. Channel filter 150 may have a variablebandwidth and may be a narrowband channel filter to enable reduced noiseeffects. Channel filter 150 may be controlled to be a narrow bandwidthchannel filter for use in weak signal conditions in order to reduce thenoise effect; while a broad bandwidth channel filter may be used atstrong signal levels. In one embodiment, MCU 190 measures the signalstrength and controls the filter bandwidth accordingly. The filteredoutput is in turn provided to a FM demodulator 155 for FM demodulation.

The receive chain continues from FM demodulator 155, the output of whichis provided to an impulse blanker 157, and then in turn to a DC cutter160, to a de-emphasis block 162 and to an interpolator 164 to increasethe sampling rate of the demodulated FM data (i.e., the voice messagedata), which is then converted to an analog signal in DAC 165, which inturn is coupled off-chip to a speaker.

Furthermore, the FM demodulated data is also provided to a SAME (AFSK)demodulator 170 which may perform SAME demodulation to thus extract theSAME message for transmission to a host controller 195 to which receiver100 is coupled. The SAME message may correspond to a text message thatcan be displayed on a display of a radio or other output device. SAMEdemodulator 170 may also generate a bit error rate (BER) signal, whichcan be provided to MCU 190. Further details of a SAME demodulator inaccordance with one embodiment of the present invention will bedescribed below.

Note that receiver 100 may include multiple WAT detectors 158 and 175which can detect a WAT message and provide an appropriate response,e.g., a WAT interrupt signal to host controller 195.

As further shown in FIG. 2, the FM demodulated signal may also beprovided to a feedback loop that includes an automatic frequency control(AFC) loop filter 180 and fine tune controller 185, which together mayfinely control the frequency provided to digital mixer 145 to enable themixing of the incoming digital data in digital mixer 145 to provide finefrequency tuning and compensate for any noise introduced by stepfrequency changes that occur in analog mixer 110 as a result of a changeto the LO frequency. Thus fine tune controller 185 may provide finetuning based on process, voltage and temperature (PVT) effects, as wellas step frequency changes, to enable small frequency errors. While shownwith this particular implementation in the embodiment of FIG. 2, thescope of the present invention is not limited in this regard.

Referring now to FIG. 3, shown is a block diagram of a high level viewof a demodulator in accordance with an embodiment of the presentinvention. As shown in FIG. 3, demodulator 200, which may be a SAME(AFSK) demodulator, is coupled to receive incoming FM demodulatedsignals. In one embodiment, such signals may be received from FMdemodulator 155 as shown in FIG. 2 (and through the rest of thedemodulated signal chain which in turn is coupled to SAME demodulator170 of FIG. 2). The incoming demodulated signals are provided to adecimator 210 which may reduce a sampling rate of the incoming signalsfrom 64 KS/s to 16 KS/s, although the scope of the present invention isnot limited in this regard. The resampled signals are provided to amatched filter/pulse forming network 220, details of which will bedescribed further below. The combined filtered signals, which may beoutput at the same sampling rate as the input, are provided to avariable interpolator 225, which is controlled by a timing control unit230 to provide interpolated samples (i.e., soft decisions) at a rate of520.83 symbols per second (S/s). Thus the output of variableinterpolator 225 may be generated at the bit rate of the SAME messages,i.e., 520.83 bits per second.

Referring still to FIG. 3, the interpolated symbols are provided to apreamble correlator 240, which may continuously run to extract a burstySAME message within the incoming radio transmission. More specifically,as will be described further below, preamble correlator 240 maydetermine when a preamble portion of a SAME message, i.e., a 128-bitpredetermined data pattern, is received and may generate a preamblesynchronization (preamble sync) signal therefrom. Furthermore, preamblecorrelator 240 may generate a bit error rate (BER) estimate. After apreamble is detected, either a start of message (SOM) or an end ofmessage (EOM) signal can be detected by comparing the received datapattern with the known SOM and EOM patterns. In some embodiments, theSOM signal may be detected in preamble correlator 240, and the EOMsignal in EOM detector 250.

The interpolated symbol data from variable interpolator 225 is furtherprovided to a soft decision diversity combiner 245 which, as will bedescribed further below, may combine soft decisions from the threerepeated transmissions of the identical SAME message to thus generate ahard decision for each bit of the message. This message information maythen be provided, e.g., off-chip, to a host controller or otherprocessor to generate a text message based on this information.

Referring now to FIG. 4, shown are further details of a SAME demodulatorin accordance with an embodiment of the present invention. Shown in moredetail in FIG. 4 is the matched filter/pulse forming network 220, whichis expanded to show that a plurality of digital mixers 222 _(a)-222 _(d)are coupled to receive the FM demodulated signal and mix it with acorresponding complex signal. The outputs, which are phase-delayedversions of the input signal, are each provided to a correspondingmatched filter 224 _(a)-224 _(d). The output of each matched filter isin turn is provided to an exponential calculator 226 _(a)-226 _(d),which performs an exponential function, e.g., raising the incomingfiltered value by a power of two, for example. The complex values areprovided in pairs to a first pair of combiners 227 _(a)-227 _(b), whichare differentially combined in a final combiner 228 to provide pulseshaping.

Furthermore, the variable interpolation and timing control unit of FIG.3 is expanded in FIG. 4 to show that timing control unit 230 forms afeedback loop including a timing error detector 232, a loop filter 234,and an interpolator controller 236, which may include a numericallycontrolled oscillator (NCO) to provide a bit clock to controlinterpolator 225. As will be discussed further below, loop filter 234 iscontrolled based on detection of a preamble portion of a SAME message(via the preamble sync signal). Interpolator 225 may operate to resamplethe incoming signals to a sampling rate of twice that of the actual bitdata, i.e., 1041.66 S/s. These resampled symbols are provided to adecimator 244, where they are resampled to the bit rate of 520.83 S/s.

FIG. 4 further shows expanding of the preamble correlation unit.Specifically, a hard decision unit 238 generates hard decisions from theincoming bit stream, which it provides to preamble correlator 240 todetermine the presence of an actual preamble having the predeterminedbit pattern. Because of the bursty nature of the SAME messages, preamblecorrelator 240 operates at all times. A correlated output fromcorrelator 240 is provided to a threshold unit 242, which may performnoise thresholding. When a valid preamble is detected, a preamble syncsignal is sent to control both loop filter 234 and EOM detector 250.Threshold unit 242 may further generate a BER estimate based on thenoise present in the signal.

In the preamble acquisition mode of operation, the loop gain controlsignal provided to loop filter 234 may act to operate loop filter 234 ata relatively high gain, thus, to achieve a wide closed-loop bandwidth.While the scope of the present invention is not limited in this regard,the gain of loop filter 234 may be increased 4 times in acquisitionmode, when compared to tracking mode operation. However, after a SAMEmessage is acquired by determination of the presence of a validpreamble, the loop gain control signal provided to loop filter 234 maycause it to operate at a relatively low gain, thus, resulting in anarrow bandwidth to reduce any jitter or other noise.

Note that timing error detector 232 may be implemented to controlsampling of the incoming data at a maximum eye opening position. Morespecifically, in one embodiment timing error detector 232 may operate onan incoming signal in accordance with the following equation:

−([r(n−2)−r(n)]*r(n−1))  [EQ. 1]

where n−2 and n are at the maximum positive and negative values of thesignal, and n−1 is at a zero crossing point, once the control loop haslocked.

Embodiments may perform symbol decisions in soft decision diversitycombiner 245. Such embodiments may be memory-friendly, as a costeffective DSP implementation of this combining scheme and storage of theincoming message data in a temporary buffer can be realized.Furthermore, combiner 245 may be programmable to operate in differentmodes such that the resulting output of combiner 245, which correspondsto the SAME message, can be raw message data or a processed resultcorresponding to a combined message.

Referring now to FIG. 5, shown is a detailed block diagram of a combinerin accordance with one embodiment of the present invention. As shown inFIG. 5, combiner 300 may receive incoming soft decision samples, whichmay be 16 bit samples (in one embodiment) in a resampler 305. Resampler305 may resample these 16 bits to generate a 4 bit soft bit decision.This 4 bit, soft bit decision may be provided to a soft decisioncombiner 310 which is further coupled to receive the preamble syncsignal. This signal may indicate which of the three duplicated messagesthat the sample corresponds. For example, the first preamble sync signalmay indicate that the soft decision sample is from the firsttransmission of the SAME message, i.e., a first frame of the SAMEmessage. If so, soft decision combiner 310 may provide the first samplefor storage in a data buffer 320, which may be a temporary storagewithin the DSP.

Assume that this operation proceeds in the same fashion for storage ofeach soft decision for the first SAME message, with each 4 bit samplestored in a different entry within data buffer 320. In one embodiment,data buffer 320 may have a size sufficient to store 2144 entries (i.e.,for the maximum 268 bytes of a SAME message).

Assume next that the preamble sync signal now indicates incoming softdecision samples to combiner 300 are from the second frame of the SAMEmessage. In this instance, the resampled 4 bit samples provided to softdecision combiner 310 may be combined with the corresponding entriesstored in data buffer 320 for the same soft decision sample of the firstSAME message. For example, a logical AND operation may be performedwithin soft decision combiner 310 to thus combine the soft decisions ofthe first and second frames. This combined sample may replace theoriginal first frame sample in buffer 320, thus enabling memoryfriendly, cost effective DSP implementation. A similar operation maythen be performed between this combined decision stored in data buffer320 and the third and final corresponding soft decision of the thirdmessage frame. Then this final combined soft decision, which maycorrespond to a logical ANDing of the third soft decision with thecombined soft decision (i.e., of the first and second frames), isprovided to a hard decision unit 330, which thus generates the harddecision and provides the output as the SAME message.

While described with this particular operation in the embodiment of FIG.5, the scope of the present invention is not limited in this regard andin other implementations, as mentioned above, raw SAME messages may beprovided through soft decision combiner 300 to output hard decisionsthat can be further processed, e.g., by way of a majority vote. However,using the implementation outlined above, a single bit-to-noise power(Eb/No) improvement of approximately 4.7 dB may be realized as comparedto direct hard decision decoding.

Referring now to FIG. 6, shown is a flow diagram of a method inaccordance with one embodiment of the present invention. As shown inFIG. 6, method 400 may be used to receive and combine soft bit decisionsinto a hard decision, namely the corresponding bits of a SAME message.Note that the flow shown in FIG. 6 is for a single bit of a SAMEmessage, as received three times (i.e., one bit in each of threeframes). Understand that the flow of FIG. 6 may be applied for each bitof the SAME message. As shown in FIG. 6, method 400, which may beimplemented in a DSP, e.g., in soft decision diversity combiner 300 ofFIG. 5, may proceed as follows.

First, an incoming sample of a frame of a SAME message may be receivedin the combiner (block 410). For this sample (which, as described abovein connection with FIG. 5, may be resampled from a first bit width to asecond, smaller bit width), it may be determined whether the sample isfrom a first frame of a SAME message (diamond 420). If so, the samplemay be written to a given entry in a buffer, e.g., a DSP buffer coupledto the combiner (block 450). Control then passes to diamond 460,discussed further below.

If instead the sample received is not from the first frame, controlpasses to block 430, where the sample may be combined with acorresponding buffered entry. More specifically, assume that the sampleis the first sample of a frame. Accordingly a corresponding entry in thebuffer that stores the first sample of a previous frame (or a combinedresult) may be obtained and the combiner can combine the sample withthis buffered entry. While different manners of combining these valuescan occur, in one embodiment a logical AND operation between thesevalues may occur.

Referring still to FIG. 6, the result of this combination operation maybe written into the corresponding entry of the buffer (block 440). Thatis, this result may overwrite the previous value stored in the entry,whether the original sample from a first frame or a previouscombination's result, e.g., a combination of a first and second frame.In this way, reduced memory overhead is needed. Note that in someimplementations if the combination operation is between a stored sampleand a sample of the third incoming frame, the result is not stored backto the buffer and instead is directly output from the combiner fordetermination of a hard decision.

Control then passes to diamond 460, where it may be determined whetherthe received sample is from a last frame of a SAME message. In oneembodiment, this determination may be made based on a counter value thatrecords how many times the SOM pattern has been received. From thisvalue it may be determined whether the current frame is a first, secondor third frame. If the sample is not form the last frame, control passesback to block 410, discussed above.

If the sample was of a last frame of a message, the final result thatwas generated in the combiner may be used to generate a hard decision(block 470). For example, the combiner may be coupled to a hard decisionunit that receives this final result and for each sample, generates ahard decision bit. Thus once the SOM counter reaches 3, indicating thatthe current SAME message is the third identical message, the harddecision unit begins to operate. The hard decision information, whichcorresponds to a bit of the SAME message, may be provided off-chip, suchas to a host controller or other processor that can generate a textmessage from this information. Of course method 400 may proceed insimilar fashion for each sample of the three frames of a SAME message.While shown with this particular implementation in the embodiment ofFIG. 6, the scope of the present invention is not limited in thisregard.

Referring to FIG. 7, in accordance with some embodiments of theinvention, a multimode transceiver 10, which may include weather bandreceiver 100 of FIG. 2, may be part of a multimedia portable wirelessdevice 510, which, in turn, is part of a wireless system 500. Asexamples, the wireless device 510 may be a multi-function, multi-bandradio, a cellular telephone or PDA with the capability of playing musicdownloads, part of a wireless link between a satellite antenna and aradio receiver, a terrestrial receiver, etc. Of course, wireless device510 may be a stand alone weather band radio, in other embodiments.

Among its other various functions, the wireless device 510 may storedigital content on a storage 530, which may be a flash memory or harddisk drive, as a few examples. The wireless device 510 generallyincludes an application subsystem 560 that may, for example, receiveinput from a keypad 562 of the wireless device 510 and displayinformation, such as weather-related information obtained from a SAMEmessage, on a display 570. Furthermore, the application subsystem 560may generally control the retrieval and storage of content from thestorage 530 and the communication of, e.g., audio with the multimodetransceiver 10. As shown, the multimode transceiver 10 may be directlyconnected to speakers 540 and 550 for output of audio data. As depictedin FIG. 7, the multimode transceiver 10 may be coupled by a matchingnetwork 534 to a receiver antenna 580 and may be coupled by a matchingnetwork 532 to the transmit antenna 582.

Although the wireless device 510 may include the speakers 540 and 550,it may be desirable to play sounds that are generated by the wirelessdevice 510 over a more sophisticated speaker system. Therefore, inaccordance with some embodiments of the invention, the wireless device510, via the multimode transceiver 10, may broadcast content to beplayed over an FM channel to the receiver of an adjacent stereo system500 (as an example). As shown, the stereo system 500 includes an RFantenna 504 for purposes of receiving the transmitted content from thewireless device 510.

In accordance with some embodiments of the invention, the wirelessdevice 510 may have the ability to communicate over a communicationsnetwork, such as a cellular network. For these embodiments, the wirelessdevice 510 may include a baseband subsystem 575 that is coupled to theapplication subsystem 560 for purposes of encoding and decoding basebandsignals for this wireless network. Baseband subsystem 570 may be coupledto a transceiver 576 that is connected to corresponding transmit andreceive antennas 577 and 578.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

1. A system comprising: an antenna to receive radio frequency (RF)signals including incoming weather band radio signals; an analog frontend to receive the incoming weather band radio signals from the antenna,the analog front end including: an analog mixer to mix the incomingweather band radio signals with a controllable oscillator frequency togenerate a complex downmixed signal; and an analog-to-digital converter(ADC) to convert the complex downmixed signal to a digital signal; adigital signal processor (DSP) coupled to the analog front end, whereinthe DSP includes: a first demodulator to demodulate the digital signalto generate a first demodulated signal; a second demodulator to receivethe first demodulated signal and to obtain weather band data therefrom,wherein the second demodulator includes: an interpolator to receivesamples of multiple frames of a message and generate soft decisionstherefrom; and a combiner to combine the soft decisions of the multipleframes into a hard decision corresponding to a bit of the weather banddata.
 2. The system of claim 1, wherein the second demodulator comprisesa preamble correlator to determine receipt of a preamble of the weatherband data.
 3. The system of claim 2, wherein the second demodulatorcomprises a timing controller to control a sampling rate of theinterpolator under control of the preamble correlator, wherein thetiming controller includes: a timing error detector coupled to an outputof the interpolator to control the sampling rate to be at a maximum eyeopening position; and a loop filter coupled to the timing error detectorhaving a variable gain controlled responsive to determination of receiptof the preamble, wherein a gain of the loop filter is greater in anacquisition mode than in a tracking mode.
 4. The system of claim 1,further comprising a radio receiver formed on a single semiconductor dieincluding the analog front end and the DSP, and wherein the seconddemodulator further includes: a plurality of digital mixers each toreceive the first demodulated signal and mix the first demodulatedsignal with a reference signal to generate phase delayed mixer outputs;a plurality of matched filters coupled to an output of the plurality ofdemodulators to filter the mixer outputs; an exponential generator toperform an exponential function on the filter outputs; a first pair ofcombiners to combine the exponential filter outputs; and a secondcombiner to differentially combine the outputs of the first pair ofcombiners to generate a pulse shaped signal.
 5. The system of claim 4,wherein the DSP is further adapted to demodulate incoming amplitudemodulation (AM) radio signals and FM radio signals.
 6. The system ofclaim 1, wherein the combiner is to receive a soft decision of one ofthe multiple frames and to combine the soft decision with a value in acorresponding entry of a buffer if the soft decision is not of a firstframe of the multiple frames, otherwise the combiner is to store thesoft decision in the corresponding entry of the buffer.
 7. The system ofclaim 6, wherein the combiner is to perform a first logical operation tocombine the soft decision and the value and store a result of the firstlogical operation in the corresponding entry of the buffer and perform asecond logical operation to combine the result and a soft decision of anext frame of the multiple frames and to output the combined result to ahard decision unit, wherein the hard decision unit is to generate thehard decision therefrom.
 8. A system comprising: an antenna to receiveradio frequency (RF) signals including incoming weather band radiosignals; an analog front end to receive the incoming weather band radiosignals from the antenna, the analog front end including: an analogmixer to mix the incoming weather band radio signals with a controllableoscillator frequency to generate a complex downmixed signal; and ananalog-to-digital converter (ADC) to convert the complex downmixedsignal to a digital signal; a digital signal processor (DSP) coupled tothe analog front end, the DSP comprising: a combiner to receive a softdecision sample of a specific area encoding (SAME) message of theincoming weather band radio signals and to combine the soft decisionsample with a value in a corresponding entry of a buffer coupled to thecombiner when the soft decision sample is not of a first frame of theSAME message; and a hard decision unit to receive an output of thecombiner and to generate a bit value for a bit of the SAME message fromthe output.
 9. The system of claim 8, further comprising a resampler toreceive the soft decision sample having a first bit width and providethe soft decision sample to the combiner having a second bit width, thesecond bit width less than the first bit width.
 10. The system of claim8, wherein the combiner is to perform a first logical operation tocombine the soft decision sample and the value and store a result of thefirst logical operation in the corresponding entry of the buffer. 11.The system of claim 10, wherein the combiner is to perform a secondlogical operation to combine the result and a soft decision sample of anext frame of the SAME message and to output the combined result to thehard decision unit.
 12. The system of claim 10, wherein the combiner isto receive a start of message signal and based on the start of messagesignal determine a frame number associated with the soft decisionsample.
 13. The system of claim 8, wherein the combiner is to store thesoft decision sample to the corresponding entry of the buffer if thesoft decision sample is of the first frame.
 14. A system comprising: anantenna to receive radio frequency (RF) signals including incomingweather band radio signals; an analog front end to receive the incomingweather band radio signals from the antenna, the analog front endincluding: an analog mixer to mix the incoming weather band radiosignals with a controllable oscillator frequency to generate a complexdownmixed signal; and an analog-to-digital converter (ADC) to convertthe complex downmixed signal to a digital signal; a digital signalprocessor (DSP) coupled to the analog front end, wherein the DSP is toreceive a sample of a frame of a specific area encoding (SAME) messageof the incoming weather band radio signals, determine if the sample isof a first frame of the SAME message, write the sample to an entry of abuffer if the sample is of the first frame, otherwise provide the sampleto a combiner, combine the sample with a buffered value in acorresponding entry of the buffer, and write a result of the combiningto the corresponding entry of the buffer.
 15. The system of claim 14,wherein the DSP includes a resampler to receive the sample with a secondbit width less than a first bit width.
 16. The system of claim 15,wherein the DSP is to provide the result of the combining to a harddecision unit, and generate a hard decision based on the result.
 17. Thesystem of claim 16, wherein the hard decision corresponds to a bit ofthe SAME message.
 18. The system of claim 16, wherein the DSP is toprovide the result of the combining to the hard decision unit if thecombining is of a third frame sample and the buffered value, otherwisewrite the result to the corresponding entry of the buffer.
 19. Themethod of claim 15, wherein the DSP is to determine if the sample is ofthe first frame based on a synchronization signal generated responsiveto receipt of a preamble portion of the SAME message.